JP2816525B2 - Multi-source refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage refrigerating apparatus used for connecting a plurality of refrigerating machines in multiple stages and cooling them to an extremely low temperature.

[0002]

2. Description of the Related Art Recently, the freezing storage temperature of fresh fish such as tuna has been reduced to an extremely low temperature of -60.degree. C. to -70.degree. Is used.

In this multi-stage refrigeration apparatus, the condenser of the high-side refrigerator is cooled by cooling water, and the high-side cooling coil condenses the refrigerant gas discharged from the compressor of the low-side refrigerator. By connecting to a cascade condenser of a condenser and connecting multiple refrigerators by a heat exchanger (cascade condenser), the heat load of the freezer etc. is cooled to a very low temperature by the cooler on the lower side. It is. When the refrigerators are connected in two stages, the higher-stage refrigerator becomes the first-stage refrigerator and the lower-stage refrigerator becomes the second-stage refrigerator.

In such a multi-stage refrigeration system, Freon R13 or R503 has conventionally been used as a refrigerant for the second-stage refrigeration unit. Therefore, the discharge gas compressed by the second source compressor is:
The temperature is not so high, small devices are air cooled,
Large equipment was cooled with water or sent to a cascade condenser without cooling.

[0005]

Conventionally, Freon R13 or R503 has been used as the refrigerant of the second refrigerating machine.
These refrigerants can no longer be used due to CFC regulations.
For this reason, it became necessary to use HFC23 as a substitute refrigerant. However, the temperature of the discharge gas compressed by the compressor of the HFC 23 rises by about 20 to 30 ° C. as compared with the conventional refrigerant. Therefore, in order to keep the discharge gas temperature on the second element side low, the compressor on the first element side should be a two-stage compressor,
It is necessary to lower the compression ratio or the condensing pressure of the main compressor.

It is an object of the present invention to effectively operate the above-described two-stage compressor, thereby reducing the size of the apparatus and saving energy.

[0007]

In order to achieve this object, a multi-stage refrigeration system according to the present invention is a multi-stage refrigeration system in which a plurality of refrigerators are connected in multiple stages by a cascade condenser forming a condenser. A discharge gas cooler is installed between the discharge side of the compressor and the inlet of the cascade condenser to pre-cool the discharge gas from the low-side compressor, and the high-side compressor is separated from the low-stage compressor and the high-stage compressor. After the refrigerant discharged from this high-stage compressor is liquefied by a condenser, the pressure is reduced to the suction pressure of the high-stage compressor by an expansion valve and guided to the coil of the discharge gas cooler. And heat exchange with the lower side discharge gas.

[0008]

According to the above configuration, the amount of heat of the cascade condenser cooled by the low-stage compressor of the high-stage compressor is reduced, and the high-stage compressor can be downsized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of a multi-stage refrigeration apparatus according to the present invention will be described in detail with reference to the drawings. The system diagram of FIG. 1 shows one embodiment of the multi-source refrigeration apparatus. In this figure, a first main compressor 1 is a reciprocating or screw type two-stage compressor, and a discharge pipe of a low-stage (front-stage) compressor 1a is a suction tube of a high-stage (rear-stage) compressor 1b. Connected to. The discharge pipe of the high-stage compressor 1b is connected to the inlet of the condenser 2 through which the cooling water flows through the coil 2a. The refrigerant liquefied in the condenser 2 is decompressed by an expansion valve 6 and sent to a coil 7a of a desuperheater (discharge gas cooler) 7 where heat is exchanged. The refrigerant evaporated by the desuperheater 7 is sucked into the high-stage compressor 1b.

The outlet of the condenser 2 is connected through an expansion valve 3 to the inlet of a coil 4a of an intercooler 4. The outlet of the coil 4a of the intercooler 4 is connected to the suction pipe of the high-stage compressor 1b. The outlet of the condenser 2 is connected to the inlet of the intercooler 4, and the outlet of the intercooler 4 is connected to the inlet of the coil 9 a of the cascade condenser 9 via an electromagnetic valve and an expansion valve 8. This cascade capacitor 9
The outlet of the coil 9a is connected to the suction pipe of the low-stage compressor 1a.

On the other hand, a second compressor comprising a single-stage or two-stage compressor
The discharge gas compressed by the main compressor 10 is cooled in a cooler 11 by a conventional method (water or air),
It is sent to the desuperheater 7. The outlet of the desuperheater 7 is connected to the inlet of the cascade condenser 9, and the outlet of the cascade condenser 9 is connected to the expansion valve 12.
Is connected to the inlet of the cooling coil 13a of the cooler 13 for cooling the load. The outlet of the cooling coil 13a is connected to a suction pipe of the compressor 10. The inlet of the desuperheater 7 is connected via the protective container 14 to the second main compressor 10.
Connected to the suction pipe.

In the multi-unit refrigeration system configured as described above,
After cooling the refrigerant gas discharged from the second compressor 10 by a conventional method, the refrigerant gas is sent to the desuperheater 7 and
Cooling is performed by exchanging heat with the liquefied refrigerant in the condenser 2 on the original side.
The first-source liquid refrigerant is gasified by exchanging heat with the second-source discharge gas in the desuperheater 7, and is guided to a high-stage suction pipe of the first compressor 1.

As a result, the amount of heat of the cascade condenser 9, which cools the first stage compressor 1 at a low stage, can be reduced, so that the size of the first stage compressor 1 (reduction of piston displacement) and energy saving can be reduced. Can be planned.

Next, another embodiment shown in FIG. 2 will be described. Also in this embodiment, the discharge gas compressed by the second compressor 10 is guided to the desuperheater 7 after being cooled by a conventional method. The refrigerant liquefied in the first condenser 2 is decompressed by the expansion valve 3 and guided to the coil 4a of the intercooler 4, and gasified to partially cool the low-stage refrigerant (including some liquid). The refrigerant is sent to the desuperheater 7 and exchanges heat with the discharge gas on the second source side. The evaporated primary refrigerant is
It is led to a high-stage suction pipe of the first main compressor 1.

Next, another embodiment shown in FIG. 3 will be described. The discharge gas compressed by the second compressor 10 is guided to the desuperheater 7 after being cooled by a conventional method. The refrigerant liquefied in the first condenser 2 is decompressed by the expansion valve 6,
It is sent to the desuperheater 7 and exchanges heat with the discharge gas on the second source side. The evaporated refrigerant (including a part of the liquid) is led to the coil 4a of the intercooler 4 to exchange heat. First evaporated
The original refrigerant is guided to a high-stage suction pipe of the first original compressor 1.

Next, the amount of heat radiation from the second element is set to 10,000
At 0 Kcal / h, the refrigerant circulation amount of the first main compressor 1 is compared between the conventional system and the system according to the present invention. FIG. 4 shows a Mollier diagram of the refrigerator on the first element side. In this figure, A shows a case where a reciprocating type is used for the first main compressor 1,
B shows a case where a screw type is used. FIG.
The Mollier diagram of the original refrigerator is shown.

First, in the conventional system in which the total amount of heat is cooled by the cascade condenser 9, the low stage refrigerant circulation amount = 10,000 Kcal / h / 46.53 Kca
l / Kg = 214.9 kg / h Supercooling heat = 214.9 kg / h x (112.77-9
8.59) Kcal / Kg = 3,047 Kcal / h Refrigerant volume evaporated for supercooling = 3047 Kcal / h /
35.68Kcal / Kg = 85.4Kg / h Low stage compression amount = 214.9Kg / h Middle stage compression amount = 214.9 + 85.4 = 300.3Kg / h On the other hand, in the method according to the present invention, the enthalpy difference in the condensation process Of the 60.095 Kcal / Kg, the cooling amount of the desuperheater 7 is 6 Kcal / Kg, which is 10%, so the heat amount is 10,000.
The breakdown of 0 Kcal / h is as follows: Heat of cascade condenser = 9,000 Kcal / h Heat of desuper heater = 1,000 Kcal / h Low-stage refrigerant circulation amount = 9,000 Kcal / h / 46.53 Kcal
/Kg=193.4Kg/h Supercooling heat = 193.4Kg / h × (112.77-9
8.59) Kcal / Kg = 2742 Kcal / h Amount of refrigerant evaporated for supercooling = 2,742 Kcal / h
/35.68Kcal/Kg = 76.9Kg / h Amount of refrigerant evaporated by the desuperheater = 1,000Kcal / h / 35.68Kcal / Kg = 28.0Kg / h Therefore, the amount of low-stage compression = 193.4Kg / h Middle stage compression amount = 193.4 + 76.9 + 28.0 = 28
8.3 kg / h As described above, according to the method of the present invention, the power of the first main compressor 1 and the piston displacement can be reduced by about 7% as shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, when the HFC23 is used as a substitute refrigerant for R13 or R503 in the second chiller, the refrigerant liquefied in the first condenser is expanded by the expansion valve. In this case, the pressure is reduced to the suction pressure of the high-stage compressor and heat is exchanged between the discharge gas cooler and the discharge gas on the second source side. It is possible to reduce the size and save energy.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a multi-source refrigeration apparatus according to the present invention.

FIG. 2 is a system diagram showing a main part of a multiple refrigerating apparatus according to another embodiment.

FIG. 3 is a system diagram showing a main part of a multiple refrigerating apparatus according to still another embodiment.

FIG. 4 is a Mollier diagram of the first refrigerating machine.

FIG. 5 is a Mollier diagram of the second source refrigerator.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 First-stage compressor 1a Low-stage compressor 1b High-stage compressor 2 Condenser 3 Expansion valve 4 Intercooler 6 Expansion valve 7 Desuperheater 7a Heat exchange coil 8 Expansion valve 9 Cascade condenser 10 Second element Compressor 12 Expansion valve 13 Cooler 13a Cooling coil 14 Protection container

Claims (1)

(57) [Claims] 1. A multi-stage refrigeration system in which a plurality of refrigerators are connected in multiple stages by a cascade condenser forming a condenser, wherein a low-stage compressor is provided between a discharge side of a low-stage compressor and an inlet of the cascade condenser. A discharge gas cooler for pre-cooling the discharge gas from the compressor is provided. The high-stage compressor is composed of a two-stage compressor consisting of a low-stage compressor and a high-stage compressor. The refrigerant discharged from this high-stage compressor Liquefied by a condenser, reduced by an expansion valve to the suction pressure of a high-stage compressor, and guided to a coil of the discharge gas cooler to exchange heat with a lower discharge gas.